Solid-state imaging device and camera module

ABSTRACT

A solid-state imaging device is provided. The solid-state imaging device includes a plurality of arrayed pixels, an optical inner filter layer, and a light-blocking side wall. The plurality of arrayed pixels each includes a photoelectric conversion portion and a pixel transistor. The optical inner filter layer is provided for blocking infrared light and formed facing to a light-receiving surface of the photoelectric conversion portion of a desired pixel among the arrayed pixels. The light-blocking side wall is formed on a lateral wall of the optical inner filter layer.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a Continuation application of the patent applicationSer. No. 12/153,041, filed May 13, 2008, which claims priority fromJapanese Patent Application JP 2007-171008 filed in the Japanese PatentOffice on Jun. 28, 2007, the entire contents of which being incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging device,particularly, a solid-state imaging device, for example, a MOS imagesensor in which a photoelectric conversion portion and a pixeltransistor are included in a pixel. In addition, the present inventionrelates to a camera module including such a solid-state imaging device.

2. Description of the Related Art

Solid-state imaging devices can be roughly classified into chargetransfer solid-state imaging devices typified by CCD image sensors andamplified solid-state imaging devices typified by CMOS image sensors. Incomparison with the CMOS image sensor, the CCD image sensor may need apower supply voltage higher than that of the CMOS image sensor, becausethe CCD image sensor may require a high driving voltage for the transferof a signal electric charge.

Therefore, CMOS image sensors having advantages over the CCD imagesensors in terms of lower power source supply, power consumption, andthe like, compared with those of the CCD image sensors are mounted asthe solid-state imaging device on mobile devices, such as camera cellphones and personal digital assistants (PDFs), which have been used inlarge numbers in recent years.

The solid-state imaging device used in any mobile device or the like hasa reduced area per pixel along with miniaturization and high-resolution.In addition, the area of a photodiode to be provided as a photoelectricconversion portion is reduced along with a decrease in area of thepixel. Thus, it may result in a decrease in sensitivity or the like.Therefore, for example, for allowing a user to take a bright image of adark subject, a solid-state imaging device having a unit pixel matrixincluding pixels on which infrared light (IR) is incident and othercolor pixels with optical inner filter layers for blocking infraredlight (or inner-layer IR cut filter layers) has been known in the art(see Japanese Unexamined Patent Application Publication No.2006-190958).

FIG. 1 illustrates a CMOS image sensor without a filter layer forblocking infrared light, while FIG. 2 illustrates a CMOS image sensorprovided with a filter layer for blocking infrared light. In FIGS. 1 and2, a pixel is schematically represented only by a photodiode PD while apixel transistor is omitted for making the configuration of the CMOSimage sensor clearly understandable.

The CMOS image sensor 1 as illustrated in FIG. 1 includes an imagingarea formed of a plurality of pixels provided in a two-dimensionalarray. Each of the pixels has a photodiode (PD) 3 as a photoelectricconversion portion and a plurality of pixel transistors (MOStransistors, not shown) on the principal surface of a semiconductorsubstrate 2. A plurality of wiring layers 6 with a plurality of layeredlines 5 through an insulating interlayer 4 is formed on the principalsurface of the pixel-formed semiconductor substrate 2. Furthermore, acolor filter 7 and an on-chip micro lens 8 are formed above theplurality of wiring layers 6 through a planarizing layer (not shown).

The CMOS image sensor 11 as illustrated in FIG. 2 includes an imagingarea formed of a plurality of pixels provided in a two-dimensionalarray. Each of the pixels has a photodiode (PD) 3 as a photoelectricconversion portion and a plurality of pixel transistors (MOStransistors, not shown) on the principal surface of a semiconductorsubstrate 2. A plurality of wiring layers 6 with a plurality of layeredlines 5 through an insulating interlayer 4 is formed on the principalsurface of the pixel-formed semiconductor substrate 2. Furthermore, anoptical inner filter layer (inner-layer IR cut filter layer) 12 isformed above the plurality of wiring layers 6 for a pixel on which theincidence of infrared light should be blocked. In other words, theoptical inner filter layer 12 is formed above each of the pixels of red(R), green (G), and blue (B) but no optical inner filter layer 12 isformed above one pixel (that is, IR pixel). A buried layer 13 is formedon an area on which no optical inner filter layer 12 is formed and acolor filter 7 and an on-chip micro lens 8 are then formed through aplanarizing layer (not shown). Here, a unit pixel matrix includes fourpixels, that is, the R, G, and B pixels and the IR pixel. The colorfilter for the IR pixel is formed of a filter transmitting visible lightand infrared light.

The CMOS image sensor 11 includes the IR pixel which positively usesinfrared light, so that the sensitivity thereof can be enhanced to allowa user to take a bright image with suitable color tone, for example,when the user wishes to take a bright image of a dark subject.

SUMMARY OF THE INVENTION

As shown in FIG. 2, the above-described CMOS image sensor including theoptical inner filter layer 12 in the layer under the color filter 7 hasa larger distance H1 from the light-receiving surface of the photodiode3 to the on-chip micro lens 8, compared with the distance H2 of the CMOSimage sensor 1 without the optical inner filter layer 12 as shown inFIG. 1. The larger the distance H1 becomes, the more the collection oflight by the on-chip micro lens 8 becomes insufficient. Thus, colorlight, particularly oblique light, passed through the color filter 7 andincident on the target pixel may enter adjacent pixels of other colors.Therefore, the color mixture may occur and the property of the device,that is, color sensitivity, may decrease.

It is desirable to provide a solid-state imaging device having anoptical inner filter layer for blocking infrared light while suppressingthe occurrence of a color mixture and also provide a camera moduleincluding such a solid-state imaging device.

According to an embodiment of the present invention, there is provided asolid-state imaging device including a plurality of arrayed pixels, anoptical inner filter layer, and a light-blocking side wall. The arrayedpixels each include a photoelectric conversion portion and a pixeltransistor. The optical inner filter layer is provided for blockinginfrared light and formed facing to a light-receiving surface of thephotoelectric conversion portion of a desired pixel among the arrayedpixels. The light-blocking side wall is formed on the lateral wall ofthe optical inner filter layer.

According to another embodiment of the present invention, there isprovided a camera module including an optical lens system and asolid-state imaging device. The solid-state imaging device includes aplurality of arrayed pixels, an optical inner filter layer, and alight-blocking side wall. The arrayed pixels each include aphotoelectric conversion portion and a pixel transistor. The opticalinner filter layer is provided for blocking infrared light and formedfacing to a light-receiving surface of the photoelectric conversionportion of a desired pixel among the arrayed pixels. The light-blockingside wall is formed on the lateral wall of the optical inner filterlayer.

The solid-state imaging device according to the embodiment of thepresent invention includes a side wall with a light-blocking effectformed on a lateral wall of the optical inner filter layer. Therefore,oblique light incident on each pixel is blocked by the side wall of theoptical inner filter layer and suppressed so as not to enter adjacentpixels.

The camera module according to the embodiment of the present inventionincludes the solid-state imaging device having a side wall with alight-blocking effect. The side wall is formed on a lateral wall of theoptical inner filter layer. Therefore, oblique light incident on eachpixel is blocked by the side wall of the optical inner filter layer andsuppressed so as not to enter adjacent pixels.

According to the solid-state imaging device of the embodiment of thepresent invention, oblique incident light is blocked by the side wall ofthe optical inner filter layer and suppressed so as not to enteradjacent pixels. As a result, the occurrence of a color mixture can besuppressed. The camera module according to the embodiment of the presentinvention includes the above solid-state imaging device, so that theoccurrence of a color mixture can be suppressed while obtaining highquality images.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating main parts of an example of aCMOS solid-state imaging device according to the related-art without anoptical inner filter layer that blocks infrared light.

FIG. 2 is a schematic diagram illustrating main parts of an example of aCMOS solid-state imaging device according to the related-art providedwith an optical inner filter layer that blocks infrared light.

FIG. 3 is a schematic diagram illustrating the whole configuration of asolid-state imaging device in accordance with an embodiment of thepresent invention.

FIG. 4 is a circuit diagram illustrating an equivalent circuit of anexemplified unit pixel.

FIG. 5 is a schematic diagram illustrating the cross-sectional structureof the unit pixel.

FIG. 6 is a schematic diagram illustrating main parts of a solid-stateimaging device in accordance with a first embodiment of the presentinvention.

FIGS. 7A and 7B are plan views of an example of the arrangement of colorfilters used in an embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating an example of an opticalinner filter layer formed of stacked dielectric films for blockinginfrared light, which can be used in an embodiment of the presentinvention.

FIG. 9 is an explanatory diagram illustrating the operation of thesolid-state imaging device in accordance with the first embodiment ofthe present invention.

FIG. 10 is a schematic diagram illustrating an example of main parts ofa solid-state imaging device to be applied to an embodiment of thepresent invention.

FIG. 11 is a schematic diagram illustrating main parts of a solid-stateimaging device in accordance with a second embodiment of the presentinvention.

FIGS. 12A to 12C are schematic diagrams illustrating a first part ofprocess for producing the solid-state imaging device in accordance withthe second embodiment of the present invention, where FIGS. 12A, 12B,and 12C illustrate the respective steps of the process.

FIGS. 13D to 13F are schematic diagrams illustrating a second part ofprocess for producing the solid-state imaging device in accordance withthe second embodiment of the present invention, where FIGS. 13D, 13E,and 13F illustrate the respective steps of the process, which aresubsequent to the steps of FIG. 12.

FIGS. 14G to 141 are schematic diagrams illustrating a third part ofprocess for producing the solid-state imaging device in accordance withthe second embodiment of the present invention, where FIGS. 14G, 14H,and 141 illustrate the respective steps of the process, which aresubsequent to the steps of FIG. 13.

FIG. 15 is a schematic diagram illustrating another example of processfor producing the solid-state imaging device in accordance with thesecond embodiment of the present invention.

FIG. 16 is a schematic diagram illustrating main parts of a solid-stateimaging device in accordance with a third embodiment of the presentinvention.

FIG. 17 is a schematic diagram illustrating main parts of a solid-stateimaging device in accordance with a fourth embodiment of the presentinvention.

FIG. 18 is a schematic diagram illustrating the configuration of acamera module in accordance with an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to the attached drawings.

FIG. 3 is a schematic diagram of the whole configuration of a CMOSsolid-state imaging device (image sensor) as a solid-state imagingdevice in accordance with an embodiment of the present invention. Thesolid-state imaging device 21 of the present embodiment includes animaging area 23; and, as peripheral circuits, a vertical driving circuit24; a column-signal processing circuit 25; a horizontal driving circuit26, an output circuit 27; a control circuit 28; and the like, on asemiconductor substrate 100, such as a silicon substrate. Here, on theimaging area 23, a plurality of pixels 22 with their respectivephotoelectric conversion portions is regularly-arranged in a twodimensional array.

The control circuit 28 generates signals (e.g., a clock signal and acontrol signal) used as standards for the operation of the verticaldriving circuit 24, the column-signal processing circuit 25, thehorizontal driving circuit 26, and the like, on the basis of a verticalsynchronizing signal, a horizontal synchronizing signal, and a masterclock. The generated signals are input to the vertical driving circuit24, the column-signal processing circuit 25, the horizontal drivingcircuit 26, and the like.

The vertical driving circuit 24 includes, for example, a shift registerand selectively scans each pixel 22 per row on the imaging area 23 inthe vertical direction in succession. A pixel signal based on a signalelectric charge generated in response to the amount of light received ona photoelectric conversion portion (photodiode) 31 of each pixel issupplied to a column-signal processing circuit 25 through a verticalsignal line 29.

The column-signal processing circuit 25 is arranged for, for example,each column of the pixels 22. Signals output from the pixels 22 in onerow are subjected to signal processing, such as CDS for removing a noise(i.e., a fixed pattern noise inherent in the pixel 22) and signalamplification. A horizontal selection switch (not shown) is connectedbetween an output stage of the column-signal processing circuit 25 and ahorizontal signal line 30.

The horizontal driving circuit 26 includes, for example, a siftregister. It selects each of the column-signal processing circuits 25 inorder by sequentially outputting horizontal scanning pulses. Pixelsignals from the respective column-signal processing circuits 25 areoutput to the horizontal signal line 30, respectively. The outputcircuit 27 carries out signal processing on signals sequentiallysupplied from the respective column-signal processing circuits 25through the horizontal signal line 30.

FIG. 4 illustrates an example of an equivalent circuit of the abovepixel 22. The pixel 22 includes: a photoelectric conversion portion suchas a photodiode 31; and a plurality of pixel transistors, that is, MOStransistors. The plurality of MOS transistors includes, for example, atransfer transistor 32, a reset transistor 33, an amplificationtransistor 34, and a selection transistor 35.

The photodiode 31 carries out the photoelectric conversion of convertinglight into electric charges (here, electrons) the amount of whichdepends on the amount of light received. The cathode of the photodiode31 is connected to the gate of the amplification transistor 34 throughthe transfer transistor 32. A node electrically connecting to the gateof the amplification transistor 34 is referred to as a floatingdiffusion part FD. The floating diffusion part FD is formed at the drainof the transfer transistor 32.

The transfer transistor 32 is connected between the cathode of thephotodiode 31 and the floating diffusion part FD. The gate of thetransfer transistor 32 is turned ON when a transfer pulse pTRG isapplied to the transfer transistor 32 through a transfer line 42. As aresult, the electric charge of the photodiode 31 is transferred to thefloating diffusion part FD.

The drain of the reset transistor 33 is connected to a pixel power (Vdd)line 43 and the source thereof is connected to the floating diffusionpart FD. The reset transistor 33 is turned ON when a reset pulse pRST isapplied to the gate thereof through a reset line 44. In this ON state,the floating diffusion part FD is reset by draining the electric chargesof the floating diffusion part FD to a pixel power line 43 before thetransfer of a signal charge from the photodiode 31 to the floatingdiffusion part FD.

The gate of the amplification transistor 34 is connected to the floatingdiffusion part FD and the drain thereof is connected to a pixel powerline 43. The amplification transistor 34 outputs the potential of thefloating diffusion part FD after reset by the reset transistor 33 as areset level. Furthermore, the amplification transistor 34 outputs thepotential of the floating diffusion part FD after transfer of a signalcharge by the transfer transistor 32 as a signal level.

Furthermore, for example, the drain of the selection transistor 35 isconnected to the source of the amplification transistor 34 and thesource thereof is connected to the vertical signal line 29. Theselection transistor 35 is turned ON when a selection pulse φSEL isapplied to the gate thereof through a selection line 45. A signal outputfrom the amplification transistor 34 is relayed to the vertical signalline 29 while the pixel 22 is being selected.

Wiring lines in the lateral direction including the transfer line 42,the reset line 44, and the selection line 45 are common in the pixels onthe same row and controlled by the vertical driving circuit 24.

Note that the selection transistor 35 may be connected between the pixelpower line 43 and the drain of the amplification transistor 34 in thecircuit configuration. In the above-described example of configuration,the pixel includes four transistors. Alternatively, the pixel may havethree transistors by omitting the selection transistor.

FIG. 5 illustrates an example of a cross-sectional structure of mainparts of the pixel. A unit pixel 22 includes a photodiode (PD) 31 havinga first conductive type (e.g., n-type) charge storage area 45 and asecond conductive (e.g., p-type) semiconductor area (that is, p-typeaccumulation layer) 46 on the surface of the area 45 and a plurality ofpixel transistors (MOS transistors). The photodiode (PD) 31 and theplurality of pixel transistors are formed on a principal surface of asemiconductor substrate 100. The photodiode 31 functions as aphotoelectric conversion portion. FIG. 5 illustrates the transfertransistor 32 and the reset transistor 33 among a plurality of pixeltransistors. The transfer transistor 32 includes an n-type semiconductorarea 47 provided as a floating diffusion part FD, a photodiode (PD) 31,and a transfer gate electrode 48 formed through a gate-insulating film.The reset transistor 33 includes an n-type semiconductor area 47provided as a floating diffusion part FD, an n-type semiconductor area49, and a reset gate electrode 50 formed through a gate-insulating film.The unit pixel 22 can be separated from an adjacent pixel by anelement-separating area 51.

On the semiconductor substrate 100 on which pixels 22 are formed, aplurality of layers is formed through an insulating interlayer 53. Inthis example, three lines 54 [541, 542, and 543] made of metal filmsform the layers, making a plurality of wiring layers 55. A planarizinglayer 56 is formed on the plurality of wiring layers 55. The lines 54[541 to 543] can be formed at the area except of areas corresponding tothe photodiodes (PD) 31. Furthermore, but not shown in the figure,later-described optical elements including a color filter, an on-chipmicro-lens, and the like can be formed.

Furthermore, in the present embodiment, a sidewall having alight-blocking effect is formed on a lateral wall of an optical innerfilter layer, which blocks infrared light, arranged above the pluralityof wiring layers 55. Thus, oblique light can be prevented from passingthrough the optical inner filter layer and being incident on theadjacent pixel, while suppressing the generation of a color mixture.

Next, FIG. 6 illustrates a cross-sectional structure of the main partsof a CMOS solid-state imaging device in accordance with a firstembodiment of the present invention. In order to describe an embodimentof the present invention in a straightforward manner, a pixel isrepresented only by a photodiode PD and schematically described whileomitting pixel transistors. The same will be applied to each of otherembodiments described later.

As shown in FIG. 6, the CMOS solid-state imaging device 61 in accordancewith the first embodiment includes a plurality of pixels 22, each havingthe photodiode (PD) 31, arranged in a two-dimensional array on theprincipal surface of a semiconductor substrate 100. In addition, aplurality of layers is formed on the semiconductor substrate 100 throughan insulating interlayer 53. In this example, three layered lines 54[541, 542, and 543] form a plurality of wiring layers 55. An opticalinner filter layer 62 for blocking infrared light is formed above theplurality of wiring layers 55, corresponding to a desired pixel. Inaddition, a side wall 63 having a light-blocking effect is formed on thelateral wall of the optical inner filter layer 62.

Furthermore, a planarized insulating layer that fills a space betweenthe optical inner filter layers 62 adjacent to each other, that is, aplanarizing layer 64 is formed. A color filter 65 and an on-chip microlens 66 are formed in order on the planarizing layer 64.

As shown in FIG. 7A, in this example, the color filter 65 is laid out tohave a red (R) filter component 65R, a green (G) filter component 65G, ablue (B) filter component 65B, and a filter component which transmitsall the wavelengths of light including infrared light (hereinafter,referred to as infrared light (IR) filter component for convenience)65IR as one unit which is repetitively arranged. The pixel correspondingto the red filter component 65R is a red (R) pixel. The pixelcorresponding to the green filter component 65G is a green (G) pixel.The pixel corresponding to the blue filter component 65B is a blue (B)pixel. The pixel corresponding to the infrared-light filter component65IR is an infrared light (IR) pixel.

Another example of the color filter 65 is illustrated in FIG. 7B. Thiscolor filter 65 includes the following arrangements. That is, on thefirst row, the infrared-light filter component 65IR, the blue filtercomponent 65B, the infrared-light filter component 65IR, and the redfilter component 65 are repetitively arranged in this order in thehorizontal direction. Also, on the second row, the green filtercomponent 65G, the infrared-light filter component 65IR, the greenfilter component 65G, and the infrared-light filter component 65IR arerepetitively arranged in this order in the horizontal direction.Furthermore, on the third row, the infrared-light filter component 65IR,the red filter component 65R, the infrared-light filter component 65IR,and the blue filter component 65B are repetitively arranged in thisorder in the horizontal direction. Still furthermore, on the fourthline, the green filter component 65G, the infrared-light filtercomponent 65IR, the green filter component 65G, and the infrared-lightfilter component 65IR are arranged in this order in the horizontaldirection. In other words, the color filter 65 is designed to have arepetitive arrangement of the first to fourth rows in the verticaldirection (column direction).

The above optical inner filter layer 62 is formed so as to correspond tothree color pixels, the R pixel, the G pixel, and the B pixel, excludingthe IR pixel. As shown in FIG. 8, the optical inner filter layer 62 isformed as a stacked film made of dielectric films with differentrefractive indexes. For example, the optical inner filter layer 62 maybe a stacked dielectric film 623 in which a silicon oxide (SiO₂) film 62with a predetermined thickness and a silicon nitride (SiN) film 622 witha predetermined thickness are alternately stacked more than once.

A side wall 63 formed on the lateral wall of the optical inner filterlayer 62 is preferably made of a material having reflectivity as well asa light-blocking effect. In this example, the side wall 63 is made of ametal film. The metal film may be a tungsten (W) film, an aluminum (Al)film, titanium (Ti) film, or another metal film.

According to the configuration of the CMOS solid-state imaging device 61of the first embodiment, as described above, the side wall with alight-blocking effect (in this example, the side wall 63 formed of ametal film) is formed on the lateral wall of the optical inner filterlayer 62. As shown in FIG. 9, such a side wall 63 made of a metal filmblocks and prevents light incident on the IR pixel, particularly obliquelight Ls, from passing through the optical inner filter layer 62 on theadjacent pixel. Thus, the light can be prevented from reaching to theadjacent pixel. Furthermore, light passing through the optical innerfilter layer 62 and incident on the R pixel, the G pixel, and the Bpixel, particularly oblique light Ls′, is blocked by the side wall 63made of the metal film even if the oblique light Ls' may proceed towardthe adjacent pixel. Thus, the light can be prevented from reaching tothe adjacent pixel. Consequently, since the optical inner filter layer62 is provided, the generation of a color mixture can be suppressed evenif the distance H1 from the light-receiving surface of the photodiode PD31 to the on-chip micro lens 66 is large. In addition, the generation ofshading can also be suppressed.

Furthermore, since the side wall 63 is made of a metal film, the sidewall 63 has reflectivity. Thus, the rays of oblique light Ls and Ls' canbe reflected on the side wall 63 and then incident on the photodiode(PD) 31 of the corresponding IR pixel, R pixel, G pixel, and B pixel,respectively. The light that might pass through the optical inner filterlayer 62 is incident on the photodiode 31 of the pixel on which thelight is originally incident, so that probability of allowing light toreach to the photodiode 31 of each pixel can increase and an improvementin sensitivity can be obtained.

Therefore, taking advantage of the benefit of the optical inner filterlayer, a CMOS solid-state imaging device having high reliability whilesuppressing a color mixture can be provided.

FIG. 10 illustrates an example in which an inner-layer lens isincorporated in the CMOS solid-state imaging device having the opticalinner filter layer without a change in distance H1 from thelight-receiving surface of the photodiode (PD) to the on-chip microlens. The CMOS solid-state imaging device 81 of the present example hasa plurality of pixels 22 with their respective photodiodes (PDs) 31,which are arranged in a two dimensional array on the principal surfaceof the semiconductor substrate 100 in a manner similar to oneillustrated in FIG. 6 as described above. A plurality of wiring layers55 including a plurality of lines 54 [541, 542, and 543] stacked throughan insulating interlayer 53 is formed on the substrate 100. In addition,an optical inner filter layer 62 made of dielectric stacked films isformed above the plurality of wiring layers 55. However, theabove-described side wall 63 with a light-blocking effect is not formedon the optical inner filter layer 62.

Furthermore, a downwardly-convexed inner-layer lens 82 is formed on theinterlayer that fills a space between the optical inner filter layers 62adjacent to each other. In other words, the downwardly-convexedinner-layer lens 82 is formed so as to correspond to the photodiode 31of the IR pixel. The inner-layer lens 82 is formed of a first interlayer83 and a second interlayer 84 which have different refractive indexes N.In this example, the first interlayer 83 is formed of a BPSG (boronphosphorous silicate glass) film and the second interlayer 84 is formedof a silicon nitride (SiN) film having a refractive index N higher thanthat of the BPSG film, thereby forming the downwardly-convexedinner-layer lens 82. Furthermore, a color filter 65 and an on-chip microlens 66 are formed through a planarizing layer.

According to the configuration of the CMOS solid-state imaging device 81as described above, the interlayer between the optical inner filterlayers 62 adjacent to each other is provided with thedownwardly-convexed inner-layer lens 82. Accordingly, the probability ofallowing the light to reach to the photodiode 31 of the IR pixel canincrease and an improvement in sensitivity can be ensured. Besides, theinner-layer lens 82 is formed between the optical inner filter layers 62adjacent to each other. Therefore, an inner-layer lens can beincorporated without an increase in distance H1 from the light-receivingsurface of the photodiode 31 to the on-chip micro lens 66.

FIG. 11 illustrates a CMOS solid-state imaging device in accordance witha second embodiment of the present invention. This CMOS solid-stateimaging device is provided with the inner-layer lens 82 shown in FIG.10. In the CMOS solid-state imaging device 67 of the present embodiment,an optical inner filter layer (IR cut filter layer) 62 is formed betweenthe plurality of wiring layers 55 and the color filter 65, correspondingto a desired pixel. In addition, a side wall 63 with a light-blockingeffect (in this example, a side wall formed of a metal film) is formedon the lateral wall of the optical inner filter layer 62. Then, adownwardly-convexed inner-layer lens 82 as shown in FIG. 10 is formed onthe interlayer between the optical inner filter layers 62 adjacent toeach other, corresponding to the photodiode 31 of the IR pixel. Theinner-layer lens 82 includes a first interlayer 83 (in this example, aBPSG film) and a second interlayer 84 (in this example, a siliconnitride film) having a refractive index higher than that of the firstinterlayer 83. Other structural components of the CMOS solid-stateimaging device 67 are identical with those illustrated in FIG. 6 asdescribed above, so that the same reference numerals will be added tothe structural components corresponding to those of FIG. 6 to omitoverlapping description.

According to the configuration of the CMOS solid-state imaging device 67in accordance with the second embodiment, the side wall 63 made of themetal film is formed on the lateral wall of the optical inner filterlayer 62, in a manner as illustrated in FIG. 6, so that oblique light isblocked by and reflected from the side wall 63. Therefore, the light canbe prevented from reaching to the adjacent pixel and the generation of acolor mixture can be suppressed and reduced while increasing theprobability of allowing the light to reach to each of the photodiodes 31of the R pixel, the G pixel, the B pixel, and the IR pixel. Thus, animprovement in sensitivity can be ensured. Furthermore, thedownwardly-convexed inner-layer lens 82 is formed on the interlayerbetween the optical inner filter layers 62 adjacent to each other, sothat the inner-layer lens 82 can be incorporated without an increase indistance H1 from the light-receiving surface to the on-chip micro lens66. Thus, the probability of allowing the light to reach to thephotodiode 31 of the IR pixel can increase and an improvement ofsensitivity can be attained.

Next, as an embodiment of the present invention, FIGS. 12 to 14illustrate a method of producing the CMOS solid-state imaging device 67of the above second embodiment.

First, as shown in FIG. 12A, a device-separating area (not shown), aplurality of pixels 22 with photodiode (PD) 31, and the like are formedon the principal surface of the semiconductor substrate 100, followed byforming a plurality of wiring layers 55 including the insulatinginterlayer 53 and a plurality of lines 54 [541, 542, and 543]. Thewiring lines 54 can be formed of a conductive film with a light-blockingeffect, such as a Cu line or Al line. Furthermore, the optical innerfilter layer 62 formed of a plurality of the layered dielectric films isformed above the plurality of wiring layers 55, corresponding to the Rpixel, the G pixel, and the B pixel except of the IR pixel.

Next, as shown in FIG. 12B, a light-shielding material film 63A (in thisexample, a metal film of tungsten (W) or aluminum (Al)) is formed in apredetermined film thickness so that the film can extend along thesurface of the optical inner filter layer 62.

Next, as shown in FIG. 12C, the light-shielding material film 63A issubjected to an etch-back process to form the light-shielding materialfilm 63 (in this example, a side wall 63 formed of a metal film) on thelateral wall of the optical inner filter layer 62.

Next, as shown in FIG. 13D, a first interlayer 83 (in this example, aBPSG film) with a first refractive index is formed on the whole surfaceof the substrate 100 including the surface of the optical inner filterlayer 62. The first interlayer 83 is formed so that it can fill a spacebetween the optical inner filter layers 62 adjacent to each other.Therefore, the surface of the first interlayer 83 is provided withirregularity.

Next, as shown in FIG. 13E, a photoresist film 86 is formed on the firstinterlayer 83 so that the surface of the first interlayer 83 can beplanarized by filling the irregular portions on the surface thereof.Here, the etching rate of the first interlayer 83 is equal to that ofthe resist film 86.

Next, the photoresist film 86 and the first interlayer 83 are etchedback to the height shown by the broken line 87 in FIG. 13E to form thesurface-planarized first interlayer 83 as illustrated in FIG. 13F.

Next, as shown in FIG. 14G, a photolithography technique and an etchingtechnique are employed to form a resist mask 88 in a positioncorresponding to each of the optical inner filter layers 62 on the firstinterlayer 83. The resist mask 88 is formed so that it can be providedwith an area somewhat larger than the area of the optical inner filterlayer 62 on which the side wall 63 is formed, when seen from the plane.Next, as shown in FIG. 14H, a chemical dry-etching process or the likeis carried out on the first interlayer 83 through the resist mask 88 toisotropically remove the first interlayer 83. Therefore, a concavedportion 89 having a concavely-curved surface with a desired curvature isformed on the first interlayer 83 between the optical inner filterlayers 62.

Next, as shown in FIG. 14I, a second interlayer 84 (in this example, asilicon nitride (SiN) film) having a refractive index higher than thatof the first interlayer 83 is formed on the whole upper surface of thefirst interlayer 83 so that the concaved portion 89 can be filledtherewith. Subsequently, an etch-back treatment is carried out to form asurface-planarized second interlayer 84. A downwardly-convexedinner-layer lens 82 is formed of the first interlayer 83 and the secondinterlayer 84 that fills the concaved portion 89 of the first interlayer83.

In the subsequent steps, a color filter 65 and an on-chip micro lens 66are formed on the second interlayer 84 to obtain the CMOS solid-stateimaging device 67 in accordance with the second embodiment asillustrated in FIG. 11.

It should be noted that there are other methods for forming the concavedportion 89 in the first interlayer 83. As shown in FIG. 15, for example,another method includes the steps of forming an optical inner filterlayer 62 with a side wall 63, forming the first interlayer 83, andcarrying out a reflow process at a predetermined temperature making useof the irregularity of the surface. In this process, the firstinterlayer 83 reflows and the concaved portion 89 having theconcavely-curved surface with a desired curvature can be formed on thefirst interlayer 83 between the optical inner filter layers 62.

FIG. 16 illustrates a CMOS solid-state imaging device in accordance witha third embodiment of the present invention. The CMOS solid-stateimaging device 94 of the present embodiment is provided with an opticalinner filter layer 62 (IR cut filter layer) formed between a pluralityof wiring layers 55 and a color filter 65, corresponding to a desiredpixel. On the lateral wall of the optical inner filter layer 62, a sidewall 63 with a light-blocking effect (in the present example, a sidewall formed of a metal film) is formed. Furthermore, the CMOSsolid-state imaging device 94 includes a downwardly-convexed inner-layerlens 95 formed with two layers with different refractive indexes in aninterlayer between a plurality of wiring layers 55 where no layeredlines 54 [541 to 543] are formed. Specifically, the downwardly-convexedinner-layer lens 95 is formed by using an insulating interlayer 53 onthe area between layered lines 54 adjacent to each other, correspondingto each of the photodiodes (PDs) 31 of the IR pixel, the R pixel, the Gpixel, and the B pixel. Other structural components of the CMOSsolid-state imaging device 94 are identical with those illustrated inFIG. 6 as described above, so that the same reference numerals will beadded to the structural components corresponding to those of FIG. 6 toomit overlapping description.

According to the CMOS solid-state imaging device 94 of the thirdembodiment, the side wall 63 formed of the metal film is formed on thelateral wall of the optical inner filter layer 62. Therefore, in amanner similar to one illustrated in FIG. 6, oblique light can beblocked by and reflected from the side wall 63. Therefore, light isprevented from reaching to the adjacent pixel and the generation of acolor mixture can be suppressed and reduced. Moreover, probability ofallowing the light to reach to each photodiode 31 of the R pixel, the Gpixel, the B pixel, and the IR pixel can increase and sensitivity can beimproved. Furthermore, every pixel is provided with the inner-layer lens95 in the form of a downwardly-convexed shape using the insulatinginterlayer 53 between the plurality of wiring layers 55. Therefore, aCMOS solid-state imaging device incorporating an inner-layer lens can beobtained in which the probability of allowing the light to reach to thephotodiodes of all pixels can increase while the distance H1 from thelight-receiving surface of the photodiode 31 to the on-chip micro lens66 can be prevented from increasing.

FIG. 17 illustrates a CMOS solid-state imaging device in accordance witha fourth embodiment of the present invention. The CMOS solid-stateimaging device 73 of the present embodiment is formed such that a sidewall 74 with a light-blocking effect and reflectivity using a differencein refractive index is formed on the lateral wall of an optical innerfilter layer 62. The side wall 74 is formed of a film having a pluralityof layers with different refractive indexes, such as two stacked films,an insulating film 75 and an insulating film 76. In this case, the innerinsulating film 75 is formed of, for example, a silicon nitride (SiN)film with a refractive index of 2.0 and an outer insulating film 76 isformed of, for example, a silicon oxide film with a refractive index ofabout 1.4. Furthermore, a light-transmissive interlayer 77 adjacent tothe outer insulating film 76 is made of a material having a refractiveindex different from that of the outer insulating film 76. For example,it may be formed of a silicon nitride (SiN) film with a refractive indexof 2.0. The interlayer 77 may have a configuration similar to awaveguide including the outer insulating film 76 of the side wall 74 asa clad and the interlayer 77 as a core. The oblique light Ls incident onthe interlayer 77 is totally reflected on the boundary between theinterlayer 77 and the outer insulating film 76 of the side wall 74,thereby traveling to the photodiode 31. The oblique light Ls' incidenton the optical inner filter layer 62 is totally reflected on theboundary of the inner insulating film 75 and the outer insulating film76 of the side wall 74 and then travels to the photodiode 31.

Other structural components of the CMOS solid-state imaging device 73are identical with those illustrated in FIG. 6 as described above, sothat the same reference numerals will be added to the structuralcomponents corresponding to those of FIG. 6 to omit overlappingdescription.

According to the CMOS solid-state imaging device 73 of the fourthembodiment, the side wall 74 formed of a plurality of layers, theinsulating film 75 and the insulating film 76, with different refractiveindexes is formed on the lateral wall of the optical inner filter layer62. In addition, the interlayer 77 with a refractive index differentfrom that of the outer insulating film 76 is formed. Therefore, such aconfiguration of the CMOS solid-state imaging device 73 allows theoblique light to be blocked by and reflected from the boundary betweenthe interlayer 77 and the side wall 74 or the boundary between theinsulating film 75 and the insulating film 76 of the side wall 74.Accordingly, light is prevented from reaching to the adjacent pixel andthe generation of a color mixture can be suppressed and reduced.Moreover, probability of allowing the light to reach to each photodiode31 of the R pixel, the G pixel, the B pixel, and the IR pixel canincrease and sensitivity can be improved.

Alternatively, the CMOS solid-state imaging device 73 of the fourthembodiment may have a configuration using a combination of inner-layerlenses 82, 95, or the like shown in FIG. 10 and FIG. 16 as describedabove.

Furthermore, in the embodiments illustrated in FIGS. 16 and 17, aninner-layer lens 82 (see FIG. 10) may be formed above the optical innerfilter layer 62 having the side wall 63 (FIG. 16) or the side wall 74(FIG. 17), corresponding to each of the R pixel, the G pixel, the Bpixel, and the IR pixel. In addition, in the fourth embodiment asillustrated in FIG. 17, both the inner-layer lens 82 and the inner-layerlens 95 (see FIG. 10 and FIG. 16) may be formed. The CMOS solid-stateimaging device of such embodiment includes the optical inner filterlayer 62 provided with the side wall 63 or 74 having a light-blockingeffect. Thus, the generation of a color mixture can be suppressed andreduced. Furthermore, probability of allowing the light to reach to thephotodiode 31 of each pixel can increase and sensitivity can beimproved.

The CMOS solid-state imaging device 61 shown in FIG. 6 can be producedaccording to the steps shown in FIGS. 12A to 13F as described above.

The CMOS solid-state imaging device 94 shown in FIG. 16 can be producedaccording to the steps shown in FIGS. 12A to 13F after forming theinner-layer lens 95 on the insulating interlayer 53 between theplurality of wiring layers 55 according to the steps shown in FIGS. 14Gto 141 as described above.

The CMOS solid-state imaging device 73 shown in FIG. 17 can be producedaccording to the steps shown in FIGS. 12A to 13F. In other words, theside wall 74 can be formed by repeating the steps shown in FIGS. 12B to12C two times after carrying out the step shown in FIG. 12A.

In the above-described embodiments, for example, the pixel includes onephotodiode and four pixel transistors as illustrated in FIG. 4. However,not shown in the figures, the embodiments of the present invention maybe applied to a CMOS solid-state imaging device called pixel-sharingtype in which a plurality of photodiodes may share a pixel transistor.

FIG. 18 illustrates the schematic configuration of a camera module inaccordance with an embodiment of the present invention. The cameramodule 110 of the present embodiment includes the CMOS solid-stateimaging device 117 of any of the above-described embodiments, an opticallens system 111, an input/output (I/O) unit 112, a digital signalprocessor (DSP) 113, and a central processing unit (CPU) 114 into oneunit. In addition, for example, a camera module 115 may only include theCMOS solid-state imaging device 117, the optical lens system 111 and theI/O unit 112. Furthermore, a camera module 116 may include the CMOSsolid-state imaging device 117, the I/O unit 112, and the digital signalprocessor (DSP) 113.

According to the camera module of the present embodiment, the generationof an optical color mixture in the adjacent pixel can be suppressed,sensitivity can be improved, and a bright image of a dark subject can betaken using infrared light.

Furthermore if the CMOS solid-state imaging device according to anembodiment of the present invention is applied to an imaging camera, thegeneration of an optical color mixture in the adjacent pixel can besuppressed, sensitivity can be improved, and a bright image of a darksubject can be taken using infrared light.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

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 8. An imaging device, comprising: a pixel arraycomprising a plurality of pixels, each pixel including a photodiode; anoptical inner filter layer disposed between a wiring layer and a colorfilter; a light-blocking side wall formed on a lateral wall of theoptical inner filter layer, wherein the plurality of pixels areconfigured to share at least one transistor.
 9. The imaging deviceaccording to claim 8, wherein the light blocking side wall is formed ofa metal film.
 10. The imaging device according to claim 8, wherein thelight blocking side wall is made of a material with a refractive indexdifferent from that of a light-transmissive layer between the opticalinner filter layer and an other optical inner filter layer that isadjacent to the optical inner filter layer.
 11. The solid-state imagingdevice according to claim 10, further comprising: an inner-layer lensformed between the optical inner filter layer and the other opticalinner filter layer.
 12. The imaging device according to claim 8, furthercomprising: a plurality of wiring layers formed of stacked filmsincluding a line and an insulating interlayer above the light-receivingsurface; and an inner-layer lens formed between the plurality of wiringlayers, facing to the light-receiving surface of a photoelectricconversion portion.
 13. An imaging device, comprising: a pixel arraycomprising a plurality of pixels, each pixel including a photodiode; anoptical inner filter layer disposed between a wiring layer and a colorfilter; a light-blocking side wall formed on a lateral wall of theoptical inner filter layer, wherein the light blocking side wall is madeof a metal.
 14. The imaging device according to claim 13, wherein thelight blocking side wall is made of a material with a refractive indexdifferent from that of a light-transmissive layer between the opticalinner filter layer and an other optical inner filter layer that isadjacent to the optical inner filter layer.
 15. The solid-state imagingdevice according to claim 14, further comprising: an inner-layer lensformed between the optical inner filter layer and the other opticalinner filter layer.
 16. The imaging device according to claim 13,further comprising: a plurality of wiring layers formed of stacked filmsincluding a line and an insulating interlayer above the light-receivingsurface; and an inner-layer lens formed between the plurality of wiringlayers, facing to the light-receiving surface of a photoelectricconversion portion.
 17. An imaging device, comprising: a pixel arraycomprising a plurality of pixels, each pixel including a photodiode; anoptical inner filter layer disposed between a wiring layer and a colorfilter; a light-blocking side wall formed on a lateral wall of theoptical inner filter layer, wherein the light blocking side wall is madeof a material with a refractive index different from that of alight-transmissive layer between optical inner filter layers adjacent toeach other.
 18. The imaging device according to claim 17, wherein theside wall is formed of a metal film.
 19. The solid-state imaging deviceaccording to claim 17, further comprising: an inner-layer lens formedbetween the optical inner filter layer and an other optical inner filterlayer that is adjacent to the optical inner filter layer.
 20. Theimaging device according to claim 17, further comprising: a plurality ofwiring layers formed of stacked films including a line and an insulatinginterlayer above the light-receiving surface; and an inner-layer lensformed between the plurality of wiring layers, facing to thelight-receiving surface of a photoelectric conversion portion.